Make particle group both perpendicular to normal and random
Change your Emitter Geometry Normal to 0
Be aware of [edit mode] vs [object mode]
Change your Rotation Panel / Initial Orientation to normal tangent.  This will depend on the [edit mode] orientation of your leaves.  In [edit mode] rotate your leaf by 90s degrees an an axis until you get the desired result.  You initial leaf orientiation should be lined up to the xyz axis much like your back is aligned with your spine.
Set the affect of field weights panel/ gravity to 0